I am having a similar issue with my AC200P and believe the BMS to be the issue. It’s overall pack voltage is reading over 4 Volts higher then the sum of all 16 cell’s voltages. This is causing its charging phase to terminate early. There seems to be a overall pack voltage calibration issue going on. not sure if its a firmware issue or a hardware issue on the BMS.
What FW version was on your replacement BMS? there is a menu that should show this.
by chance did you get a picture of the new BMS and capture the PCB part number and revision number?
I have a similar issue with my ac200p. Battery pack reports 52v, the board up top reports 21.5v, and the unit will not operate normally. The difference is that the lcd will not turn on so i have no way of checking for error messages. Did the BMS swap work for you? If so then it doesn’t sound like it’s a problem i can resolve on my own. Hopefully more people keep posting their experiences so others can benefit. In the meantime i have a ~900 60lb paperweight laying around. I still have a need for energy storage, guess which brand I’m not going to pick?